Safety control device



y 1963 c. 1.. MARCELLINO ETAL 3,088,516

SAFETY CONTROL DEVICE 2 Sheets-Sheet 1 Filed May 16, 1958 My mm mmm WMWn mm aw 2 M.\ urn. uixkk FM y 1963 c. MARCELLINO ETAL 3,088,516

SAFETY CONTROL DEVICE Filed y 16, 1958 2 Sheets-Sheet 2 SON'C AMPLIFIERc. Tmmsnucsa HLTER RE Hr-lea (v TRANSLSTOR L E Z AMPL\ FIER A Tram [xxUnited States Patent Office 3,088,516 Patented May 7, 1963 3,088,516SAFETY CONTROL DEVICE Carmen L. Marcellino and Walter P. Palanker,Camden,

N.J., assignors of one-third to A. Morton Shapiro, Camden, NJ.

Filed May 16, 1958, Ser. No. 735,790 6 iliaims. (Cl. 158-28) Theinvention relates to a safety control device and more particularly asafety control device for monitoring the flame of a burner mechanism.

Heretofore safety control devices have been provided for monitoring theflame of a burner mechanism, which devices have operated ineflicientlyand have failed to take into account serious malfunctioning conditionsof the burner mechanism.

It is therefore a principal object of the invention to provide a new andimproved safety control device responsive to various malfunctioningconditions of a burner mechanism for terminating the operation of themechanism.

Another object of the invention is to provide a new and improved safetycontrol device having a high degree of efficiency for rapidly detectingmalfunctions of a burner mechanism and terminating its operation.

Another object of the invention is to provide a new and improved safetycontrol device for detecting both the absence of a flame or the impropercombustion of a flame for terminating the operation of the burnermechanism.

Another object of the invention is to provide a new and improved safetycontrol device for terminating the operation of a burner mechanism whenthe flame intensity exceeds a predetermined value.

Another object of the invention is to provide a new and improved safetycontrol device adapted for utilizing either alight sensing cell or acompression wave detector such as a sonic transducer for determining thecondition of the flame of a burner mechanism.

Another object of the invention is to provide a new and improved safetycontrol device including a photo-electric cell mounting means for aburner mechanism.

The above objects as Well as many other objects of the invention areachieved by providing a safety control device comprising a flame sensingmeans for detecting the flame condition of a burner mechanism, and acontrol means connected with the sensing means and including a finstrelay terminating the operation of the burner mechanism in the absenceof a flame and a second relay terminating the operation of the burnermechanism when the flame of the burner mechanism exceeds a predeterminedcombustion rate.

The safety control device also includes a pair of thermal time delayrelays connected in series with the actuating element of a holdingcircuit and positioned across a signal source, the delay relays when intheir closed positions allowing the energization of the holding circuitwhich maintains the actuating element of the holding circuit energized.The first delay relay delivers power through the holding circuitcontacts to the ignition system of the burner mechanism and terminatesenergization of the ignition system after a predetermined interval,while another pair of contacts of the holding circuit acts to continuedriving the motor of the burner mechanism as long as the holding circuitis energized.

'Iihe sensing means may have the form of a photoelectric orphoto-voltaic cell responsive to the light generated by the flame forcontrolling the operation of the control device and causing thetermination of the operation of the burner mechanism when the flamecondition indicates abnormal operation.

The sensing means may also have the form of a compression wave detectorin the audio or supersonic range for detecting an abnormal condition ofthe flame by the amplitude and composition of frequencies generated bythe flame of the burner mechanism.

The above objects of the invention as well as many other objects of theinvention will become apparent when the following description is readtogether with the drawings, in which:

FIGURE i1 is a schematic view of a safety control device embodying theinvention,

FIGURE 2 is a diagrammatic view in block form illustrating a sonicsensing means for the device shown in FIGURE 1, and

FIGURE 3 is a sectional view illustrating the mounting of a sensingmeans in a burner mechanism housing.

Like numerals refer to like parts throughout the several views.

FIGURE 1 is a schematic view of a safety control device 1d embodying theinvention. The device Jill has a pair of input terminals 12 and 14 whichare respectively connected to input lines 16 and 1-8. The terminals 12and 14 are adapted to receive 117 volt AC. power for energizing thedevice 10. The line 16 is connected to the contact 20 of a thermal delayrelay 22, while the line 18 connects the terminal 14 to groundpotential.

The thermal delay relay 22 has a heating element 24 for activating athermally responsive armature 26 which in its deenergized state normallyengages the contact 20. The armature 26 disengages the contact 20 apredetermined period after its temperature has been increased by theenergization of the heating element 24. The thermal delay relay 22 is ofthe type requiring a one to two minute delay to open the circuit betweenits contact 20 and armature 26.

A second thermal delay relay 28 may be identical to the thermal delayrelay 22. The contact 30 of the delay relay 2 8 is connected with thearmature 26 of the relay 22 and its armature 32 is connected to groundpotential through the primary winding 34 of a transformer 36 of aholding circuit 38. The heating element 40 of the relay '28 is connectedin series with the heating element 24 of the relay 22 and are bridgedbetween a line 42 and ground potential.

One end of the secondary winding 42 of the transformer 36 is connectedwith a line 44, while its other end is joined to the terminal 46 of athermostat 48.

The thermostat 48 comprises a contact 50' joined with the terminal 46and a thermally responsive bimetallic element 52 which is positioned toengage the contact 50 at temperatures below a predetermined value. Thearmature 52 is connected to a terminal 54, so that a circuit iscompleted between the terminals 46 and 54 when the temperature sensed bythe thermostat 48 is below a predetermined value.

The terminal 54 is connected by a line 56 with the armature S8 of areset relay 6!). The armature 58 of the reset relay 60 normally engagesa contact 62. When the reset relay 60 has its armature 58 in its opencontact position, the energization of its actuating coil 66 moves itsarmature 58 into engagement with its contact 62. The actuating coil 66of relay 60 is energized by the closing of the normally open push buttonswitch 68 which closes a circuit from the line 16 through the winding ofcoil 66 to ground potential.

The contact 62 of the relay 61) is joined with the line 44 by the line70 which is connected in series with the actuating coil 72 of theholding relay 74- of the circuit 38.

The first armature 76 of the holding relay 74 is connected with the line16 and engages its contact 78 when the coil 72 is energized. The contact78 is connected with the ungrounded end of the primary winding 34 of thetransformer 36.

The second armature 80 of the relay 74 is also normally open and engagesits contact 82 upon the energization of the actuating coil 72. Thearmature 80 of relay 74 is connected to the armature 26 of the delayrelay 22 and the contact of the delay relay 28, while its contact 82 isreturned to ground potential through the primary of an ignitiontransformer 84 of a burner mechanism 86. The secondary winding of thetransformer 84 may be connected in the usual manner with a pair ofelectrodes 88 such as those commonly used in oil or gas burnermechanisms for igniting the fuel dispensed by the burner mechanism.

A third armature 90 of the holding relay 74 is also connected with theline 16 and engages its contact 92 when its actuating coil 72 isenergized. The contact 92 is joined with line 42 for return to groundpotential through the series connected heating elements 40 and 24respectively of the delay relays 28 and 22, while also being returned toground potential through the motor 94 of the burner mechanism 86. Themotor 94 is of the usual type .utilized for providing a fuel pressureand may also be used for energizing a blower for mixing air in theproper proportions with the fuel to be burned. The burner mechanism 86may be of the type known in the art, in which the motor 94 iscontinuously energized during the operation of the burner, while theelectrodes 88 provide a spark for initially igniting the combustiblemixture and after a predetermined period may have their operationterminated.

The line 44 is also connected to the cathode of a crystal diode 96 whichhas its anode returned through a charging capacitor 98 to the line 70.

The anode of diode 96 is also connected by a line 100 to one end of theactuating coil 102 of a control relay 104, while the other end of theactuating coil 102 is connected to a collector electrode 106 of atransistor 108. The transitsor 108 may be of the PNP type. The controlrelay 104 has a contact 110, and an armature 114 which is biased toengage contact 110 when the actuating coil 102 is deenergized. When theactuating coil 102 of the relay 104 is energized, the armature 114disengages the contact 110.

An overload control relay 116 has its actuating coil 118 connected inparallel with the actuating coil 102 of the control relay 104.Thearmature 122 of the relay 1 16 normally disengages the contact 124except when its actuating coil 118 is energized, at which time itengages its contact 124. Contact 124 connects to armature 114 and line70.

The transistor 108 includes an emitter electrode 126 which is connectedto the line 70, and a base electrode 128 which connects to an inputterminal 130 through a variable resistor 132. The resistor 132 has anadjustable contact 134 with a shorting conductor 136.

A flame sensing means such as a photoelectric cell 136 is connectedacross the terminal 130 and a second input terminal 138 which is joinedwith the line 70. The photo-cell 136 may be of the photo-voltaic typegenerating a voltage signal responsive to the light intensity from theflame of the burner mechanism 86. Such a cell 136 may be a barrierselenium type.

The contact 110 of relay 104 and the armature 122 of relay 116 areconnected to a line 140 which is joined to the heating element 142 of anormally open thermal delay control relay 144. The heating element 142of relay 144 is connected between lines 140 and 44-, while its armature146 is joined with the line 16. The armature 146 normally disengages itscontact 148 except after a predetermined period of energization of itsheating element 142. The time delay of the control relay 144 ispreferably approximately three seconds. The contact 148 is connected toground potential through the actuating coil 150 of a shuhofi relay 152.

The shut-oif relay has an armature 154 which may assume either a left orright position. The armature 154 of the relay 152 is mechanically linkedwith the armature 58 of the reset relay 60 so that the armature 58engages its contacts 62 when the armature 154 is in its right position,and the armature 58 engages its contact 64 when the armature 154 is inits left position. Upon energization of its actuating coil 150, therelay 152 causes its armature 154 to assume its left position.

For the purpose of illustration, the safety control device 10 will bedescribed in connection with a burner mechanism 86 of the oil burningtype, although it may be utilized with a gas burner, acetylene torch,and other similar mechanisms for providing shut down of the mechanismsin the event of its malfunctioning for increasing the safety ofoperation of such devices.

Consider the safety control device 10 with its relays and contacts asshown in FIGURE 1. When the thermostat senses a temperature below apredetermined value, it closes the circuit between its terminals 46 and54. With energization supplied to the input terminals 12, 14 and thedelay relays 22 and 28 in their closed positions, energization issupplied to the input winding 34 of the transformer 36. Thereby, thesecondary winding 42 of the transformer 36 energizes the actuating coil72 of the holding relay 74 through the thermostat 48 and the reset relay60.

The armatures of the holding relay 74 assume their closed or contactingpositions as long as its actuating coil 72 remains energized. In thiscondition with the armature 76 closed the line 16 is connected directlywith the primary winding 34 of the transformer 36 for maintaining theactuating coil 72 of the holding relay 74 in its energized conditionirrespective of the conditions of the delaying relays 22 and 28.

The closed position of the armature of the holding relay 74 completesthe circuit through contact 20 and armature 26 of the delay relay 22 inits closed condition to the ignition transformer 84 of the burnermechanism 86. This results in the generation of sparks by the electrodes 88 for the initiation of combustion of the fuel dispensed by theburner mechanism 86.

The closing of the armature with the holding relay 74 in its energizedcondition, connects the line 16 with the line 42, thus, energizing theheating elements 40 and 24 respectively of the delay relays 28 and 22.At the same time, the completion of the circuit between the lines 16 and42 supplies power to the motor 94 initiating and continuing theoperation of the burner mechanism 86 in dispensing fuel mixture forignition by the electrodes 88.

After the holding relay 74 has been energized for approximately one totwo minutes the heating element 24 of the delay relay 22 sufficientlyraises the temperature of its armature 26 to cause it to disengage itscontact 20. This results in the termination of energization of theignition transformer 84 which has had more than ample time to initiatecombustion of the fuel. The delay relay 28 operates substantially in thesame manner as the relay 22, so that its armature 32 disengages itscontact 30 at approximately the same time to prevent cnergization of theignition transformer 84 through the contact 78 of the holding relay 74.However, it is noted that the motor 94 continues to be energized andallows the continued operation of the burner mechanism 86.

It is noted that the diode 96 and capacitor 98 form a rectifying circuitwhich is directly connected across the energizing coil 72 of the holdingrelay 74. Thus, the capacitor 98 provides a direct current voltageacross it during the period of energization of the actuating coil 72.

If after the holding relay 74 is actuated, the burner mechanism 86operates properly and fuel is ignited almost immediately, thephoto-electric cell 136 generates a voltage which is delivered to thebase electrode 128 of the transistor 108. The voltage delivered by thephoto-electric cell 136 is such that it increases the conductivitybetween the emitter and collector electrodes 126, 106 of the transistor108 with an increasing intensity of light generated by the flame of theburner mechanism 86. Since the control relay 104 is highly sensitive,requiring a low energizing current for its actuating coil 102, thepresence of a flame which is detected by the photo-electric cell 136'allows it to become activated. This results in the disengagement of itsarmature 114 from its contact 110. However, should the flame fail toappear or become extinguished, the signal produced by the photo-electriccell 136 is insuflicient to allow the energization of the relay 104.This causes the armature 114 of relay 104 to remain in engagement withits contact 110 allowing the energization of the heating element 142 ofthe control delay relay 144. Unless the flame appears withinapproximately three seconds after such a failure, the heating element142 raises the temperature of the temperature sensitive armature 146 toa sufiicient degree to cause it to engage its contact 148.

Closing the relay 144 results in the energization of the shut-ofi relay152 which by its coupled arrangement with the reset relay 60 opens thecircuit from the transformer winding 42 to the energizing coil 72 of theholding relay 74. This deenergizes the holding relay 74 terminating theoperation of the burner mechanism 86.

The three second delay interval provided by the control delay relay 144is sufliciently long to allow the burner mechanism 86 to ignite itsflame under proper operating conditions, and short enough to providealmost immediate shut-off of the burner mechanism 86 in the event offailure of its combustible mixture to ignite Within the safety period.The delayed ignition of the combustible fuel is thereby prevented, whichis especially important since such combustion may result in an explosionand ex-. tensive damage because of the presence of the unburneddispensed fuel.

In the case where the flame of the burner mechanism 86 is ignited Withinthe required period, energization of the heating element 142 of thedelay relay 144 is terminated and the operation of the mechanism 86continues.

Where the fuel mixture is improper resulting in a higher rate ofcombustion than is normal, the photo-electric cell 136 will generateproportionally greater output voltage. This will result in the passingof an increased current through the transistor 108. An overload relay116 is actuated when the current through its actuating coil 118 is abovea predetermined value corresponding to the said flame condition. At suchtime its armature 122 is activated to engage the contact 124 whichsimilarly results in the energization of the heating element 142 of thecontrol delay relay 144. After the required three second delay interval,the delay relay 144 is closed. This energizes the shut-oif relay 152which operates to actuate the reset relay 60 for deactivating theholding relay 74 and terminating further operation of the burnermechanism. 86'.

The adjustable resistor 132 is utilized for setting the values for whichthe safety control device 18 will operate to terminate the operation ofthe burner mechanism 86.

It is noted that after the termination of operation of the burnermechanism 86 due to a failure, the system will not allow furtheroperation unless the push button reset switch 68 is manually operatedfor resetting the relay 66. This prevents further automatic operationuntil proper remedial action has been taken by the supervisorypersonnel.

The delay relays 22, 28 also act to prevent the opercontacts 20, 38.Thereby, in the event of a failure due to a failure or after a normalburning operation, until a delay period of one to two minutes. This isthe time necessary for their armatures 26, 32 to have their temperaturessufficiently reduced to lose contact with their, contacts 20, 38.Thereby, in the event of a failure due to faulty ignition, the immediateignition of the fuel saturated burner is prevented increasing the safetyattained.

When the burner. mechanism 86 is operating properly, and the temperaturesensed by the thermostat 48 is sufficiently raised, it opens the circuitbetween its contacts 46 and 54 terminating the energization of theholding relay 74 and ending the heating cycle of the burner mechanism86. The thermostat 48 thus causes the starting and stopping of theburner mechanism 86 to appropriately control the burner mechanism 86 inaccordance with the temperatures sensed.

Thus, the safety control device 10 operates both to terminate furtheroperation of the burner mechanism 86 when it fails to produce a flameafter it has been energized for a predetermined period as well asterminating [the operation of the burner mechanism 86 when the flamewhich is produced is abnormal, such as when the mixture is improper andthe light intensity indicative thereof exceeds a predetermined value. Ofcourse, the safety control device 10 may be provided with sensing meansfor determining other abnormal parameters of the generated flame as willbe now described in connection with FIG- URE 2.

FIGURE 2 discloses a sensing means 160* comprising a sonic transducer162 which may be positioned in the exhaust of a burner systemimmediately before the stack. The signal provided by the sonictransducer is delivered to an amplifier filter 164 which delivers itsoutput to a signal rectifier 166. The signal from the rectifier 166 maybe further amplified by a transistor amplifier 168 and delivered to itsoutput leads 170, 172. The output leads 170, 172 may be connected to theterminals 138 respectively in FIGURE 1 in place of the photo-electriccell 136.

The flame of the burner mechanism 86 produces a characteristic audiocompression wave or signal having a spectrum with certain frequencyamplitudes which vary with the various conditions of the flame. Suchwave signals are detected by the sonic transducer 162. The am plifierfilter 164 has a selected frequency range which is utilized fordetermining the condition of the flame. It also operates to eliminatesuch frequencies which are not generated by the normal action of theflame but by other means which are independent of the operation of thesys- Item and would result in interference. The rectifier 166 produces adirect current signal corresponding to the amplitudes of the frequenciestransmitted by the filter 164. This signal is delivered by the amplifier168 to the terminals 130, 138 of the safety control device 10 for itsoperation in the manner already disclosed in connect-ion with thephoto-electric cell 136.

Thus if the flame fails to appear within the three second delayinterval, the sonic waves within the range of the filter 164 are absent,so that a signal is delivered causing the device 10 to shut-down andprevent operation of the burner mechanism 86. Should the flame appearwithin the required time, then the sonic transducer 162 providesfrequency signals which are passed by the filter 164 to the rectifier166 which provides a signal allowing the burner 86 to continue itsoperation under the control of the thermostat 48. Should the flameproduced by the mechanism 86 be abnormal, so that the frequenciesgenerated do not correspond to that range which is passed by the filter164 the burner mechanism 86 will likewise be shut-down. Should theamplitude of the frequencies detected by the transducer 162 and passedby the filter 164 exceed a predetermined normal value, the rectifier 166will provide a signal of increased amplitude which will activate theoverload relay 116, also causing the shut-down of the burner 86.

Although the transducer 162 has been described as detecting sonicfrequencies, such device may be utilized for detecting supersonicfrequencies which may be characteristic of the flame produced by theburner mechanism 86.

It is further noted that the operation of the safety control device 10provides constant monitoring of the opera tion of the burner mechanism86. Thesafety of the device is further increased, in that should therebe a failure of the sensing means 136 or 160, the lack of production ofthe appropriate signal will result in the automatic shutdown at theburner mechanism 86. Thus the safety control device 10 not only monitorsthe burner device 86 but has a self-monitoring feature.

In this connection, the formation of soot or other such material in thecombustion chamber and its ducts, which may cause dangerousobstructions, may be detected by the appropriate positionings of theflame sensing means. Thus if the formation of soot prevents thedetection of the flame, the safety control device 10, as previouslyexplained, will result in the termination of the operation of the burnermechanism 86 requiring supervisional action to allow the operation ofthe burner mechanism 86.

FIGURE 3 discloses a portion of a burner mechanism 86 including a blasttube or housing 180 having a sub stantially cylindrical wall structureand an opening 182 in its end 184. The opening 182 is provided to allowthe production of a flame within the chamber of a furnace. The end 184of the housing 180 may be inserted through an opening 186 formed in thewall 188 (shown in dashed lines) of a furnace. The walls 188 inaccordance with customary practice may be made of refractory material.

Within the housing 186 an oil fuel line 190 is positioned with its spraynozzle 191 positioned approximate the opening 182 and behind a pair ofelectrodes 88. The electrodes 88 form a gap at their ends for producingsparks to ignite the discharged fuel emanating from the nozzle 191 ofthe oil line 190. The electrodes 88 may be positioned in parallel oneach side of the oil fuel line 190 and provided with outer insulatingtubes 192. The outer surfaces of the insulating tubes are engaged by across bar or bracket 194 for securing them with the oil line 190. Thebracket 194 which is positioned near the opening 182 of the housing 190behind the nozzle 191 of the oil line 190, supports a flame sensingmeans which may be the photo-cell 136. The support of the cell 136 inits position within the housing 180 and proximate the flame generated bythe burner mechanism 86 is highly important. The housing 180 provides aprotective shield preventing damage to the cell 136. Furthermore, theposition within the housing 180 allows the means 136 to sense thegenerated flame without being within the furnace, but yet being in adirect path of the light radiating from the flame. At the same time, themounting of the cell 136 in this manner prevents its being coated withforeign matter and soot. This, is especially true due to the draft ofair which is forced through the blast tube housing 180 about the line190 by the blower of the usual burner mechanism for providing propercombustion and flame formation. The blast of air which circulates aboutthe sensing means 136, also acts to cool it, thus, allowing it tooperate under highly satisfactory conditions.

While a few representative embodiments of the invention have beendescribed and illustrated in detail, it is understood that the inventionis capable of various modifications and applications, not departingessentially from the spirit thereof, which will become apparent to thoseskilled in the art.

What is claimed is:

1. A safety control device for use with a burner mechanism comprising,in combination, a flame sensing means for detecting predetermined flameconditions of a burner mechanism, a control unit connected with saidsensing means including a first relay for terminating the operation ofsaid burner mechanism in the absence of a flame, a second relay forterminating the operation of said burner mechanism in response to theflame of said burner mechanism exceeding a predetermined combustionrate, said first relay comprising an actuating coil, a contact, and anarmature engaging the contact when the relay is deactivated; said secondrelay comprising an actuating coil, a contact, and an armamre engagingthe contact when the relay is activated; means activating said firstrelay during the operation of said burner mechanism upon the'detectionof a flame by said sensing means and activating said second relay duringthe operation of said burner when the flame of said burner mechanismexceeds a predetermined combustion rate; a delay relay connected withthe contacts of said first and second relays for terminating theoperation of said burner mechanism a predetermined time after thedeactivation of said first relay or the activation of said second relay,said delay relay comprising a heating element, a contact and an armaturenormally disengaging said contact and engaging said contact apredetermined time after its heating element is energized, meansconnected with the heating element of said delay relay and completing acircuit for energizing said delay relay during the operation of saidburner through either of the armatures of said first and second relaysin engagement with its respective contact, a shut off relay for theburner mechanism having an actuating coil connected with the contact ofsaid delay relay for energization, and an armature having first andsecond positions; the actuating coil of said shut off relay beingenergized by the completion of its circuit through the contact andarmature of said delay relay; said shut olf relay upon energizationactuating its armature to its second position to terminate the operationof said burner mechanism, a normally open reset switch having an openposition and a closed position, a reset relay including an actuatingcoil connected with said reset switch for energization, and an armaturehaving first and second positions; said reset relay being energized whensaid reset switch is placed in its closed position; the armature of saidreset relay assuming its first position upon energization of said resetrelay; the armature of said reset relay being coupled with the armatureof said shut off relay so that the armature of said shut off relayassumes its first position when said reset relay is energized and thearmature of said reset relay assumes its second position when said shutoff relay is energized.

2. A safety control device for use with a burner mechanism comprising aflame sensing means for detecting the flame condition of a burnermechanism; a control unit connected with said sensing means andincluding a first relay for terminating the operation of said burnermechanism in the absence of a flame and a second relay for terminatingthe operation of said burner mechanism when the flame of said burnermechanism exceeds a predetermined combustion rate; said first relay ofsaid control unit comprising an actuating coil, a contact, and anarmature engaging the contact when the relay is deactivated; said secondrelay of said control unit comprising an actuating coil, a contact, andan armature engaging the contact when the relay is activated; and inwhich said control unit includes means activating said first relayduring the operation of said burner mechanism upon the detection of aflame by said sensing means and activating said second relay during theoperation of said burner when the flame of said burner mechanism exceedsa predetermined combustion rate; and a delay relay having an actuatorconnected with the contacts of said first and second relays forterminating the operation of said burner mechanism a predetermined timeafter the deactivation of said first relay or the activation of saidsecond relay 3. The safety control device of claim 1 in which theactuator of delay relay comprises a heating element, a contact, and athermally actuated armature normally disengaging its contact andengaging its contact a predetermined time after its heating element isenergized; means connected with the heating element of Said delay relayand completing a circuit for energizing said delay relay during theoperation of said burner through either of the armatures of said firstand second relays in engagement with its respective contact.

4. The safety control device of claim 3 including a shut-off relayhaving an actuating coil connected with said delay relay forenergization, and an armature having first and second positions; theactuating coil of said shut-01f relay being energized by the completionof its circuit through the contact and armature of said delay relay;said shut-off relay upon energization actuating its armature to itssecond position to terminate the operation of said burner mechanism.

5. A safety control device for use with a burner mechanism comprising acompression wave sensing means for detecting compression waves generatedby the flame of a burner mechanism and providing an output signalproportional in intensity to the radiating intensity of the flame, afrequency filter receiving the output signal of said sensing means andproviding an output signal proportional in intensity to the radiatingintensity of a predetermined frequency range of the compression Wavesgenerated by said flame, and a control unit connected with andresponsive to the output signal delivered by said filter and includingmeans for terminating the operation of said burner mechanism when theintensity of said signal exceeds a predetermined value.

6. A safety control device for use with a burner mechanism comprising acompression wave sensing means for detecting compression waves generatedby the flame of a burner mechanism and providing an output signalproportional in intensity to the radiating intensity of the flame, afrequency filter receiving the output signal of said sensing means andproviding an output signal proportional in intensity to the radiatingintensity of a predetermined frequency range of the compression Wavesgenerated by said flame, and a control unit connected with andresponsive to the output signal delivered by said filter and includingmeans for terminating the operation of said burner mechanism, said lastnamed means terminating the operation of said burner mechanism exceptwhen the signal derived from said sensing means is within apredetermined normal range of values.

References Cited in the file of this patent UNITED STATES PATENTS1,755,390 Fischer et a1 Apr. 22, 1930 2,216,556 McGrath Oct. 1, 19402,304,489 Wetzel Dec. 8, 1942 2,375,900 DeLancey May 15, 1945 2,510,265Strobel June 6, 1950 2,630,167 Diehl Mar. 3, 1953 2,767,783 Rowell et a1Oct. 23, 1956 2,771,942 Miller Nov. 27, 1956 2,807,758 Pinckaers Sept.24, 1957 2,843,198 Beckett July 15, 1958

1. A SAFETY CONTROL DEVICE FOR USE WITH A BURNER MECHANISM COMPRISING,IN COMBINATION, A FLAME SENSING MEANS FOR DETECTING PREDETERMINED FLAMECONDITIONS OF A BURNER MECHANISM, A CONTROL UNIT CONNECTED WITH SAIDSENSING MEANS INCLUDING A FIRST RELAY FOR TERMINATING THE OPERATION OFSAID BURNER MECHANISM IN THE ABSENCE OF A FLAME, A SECOND RELAY FORTERMINATING THE OPERATION OF SAID BURNER MECHANISM IN RESPONSE TO THEFLAME OF SAID BURNER MECHANISM EXCEEDING A PREDETERMINED COMBUSTIONRATE, SAID FIRST RELAY COMPRISING AN ACTUATING COIL, A CONTACT, AND ANARMATURE ENGAGING THE CONTACT WHEN THE RELAY IS DEACTIVATED; SAID SECONDRELAY COMPRISING AN ACTUATING COIL, A CONTACT, AND AN ARMATURE ENGAGINGTHE CONTACT WHEN THE RELAY IS ACTIVATED; MEANS ACTIVATING SAID FIRSTRELAY DURING THE OPERATION OF SAID BURNER MECHANISM UPON THE DETECTIONOF A FLAME BY SAID SENSING MEANS AND ACTIVATING SAID SECOND RELAY DURINGTHE OPERATION OF SAID BURNER WHEN THE FLAME OF SAID BURNER MECHANISMEXCEEDS A PREDETERMINED COMBUSTION RATE; A DELAY RELAY CONNECTED WITHTHE CONTACTS OF SAID FIRST AND SECOND RELAYS FOR TERMINATING THEOPERATION OF SAID BURNER MECHANISM A PREDETERMINED TIME AFTER THEDEACTIVATION OF SAID FIRST RELAY OR THE ACTIVATION OF SAID SECOND RELAY,SAID DELAY RELAY COMPRISING A HEATING ELEMENT, A CONTACT AND AN ARMATURENORMALLY DISENGAGING SAID CONTACT AND ENGAGING SAID CONTACT APREDETERMINED TIME AFTER ITS HEATING ELEMENT IS ENERGIZED, MEANSCONNECTED WITH THE HEATING ELEMENT OF SAID DELAY RELAY AND COMPLETING ACIRCUIT FOR ENERGIZING SAID DELAY RELAY DURING THE OPERATION OF SAIDBURNER THROUGH EITHER OF THE ARMATURES OF SAID FIRST AND SECOND RELAYSIN ENGAGEMENT WITH ITS RESPECTIVE CONTACT, A SHUT OFF RELAY FOR THEBURNER MECHANISM HAVING AN ACTUATING COIL CONNECTED WITH THE CONTACT OFSAID DELAY RELAY FOR ENERGIZATION, AND AN ARMATURE HAVING FIRST ANDSECOND POSITIONS; THE ACTUATING COIL OF SAID SHUT OFF RELAY BEINGENERGIZED BY THE COMPLETION OF ITS CIRCUIT THROUGH THE CONTACT ANDARMATURE OF SAID DELAY RELAY; SAID SHUT OFF RELAY UPON ENERGIZATIONACTUATING ITS ARMATURE TO ITS SECOND POSITION TO TERMINATE THE OPERATIONOF SAID BURNER MECHANISM, A NORMALLY OPEN RESET SWITCH HAVING AN OPENPOSITION AND A CLOSED POSITION, A RESET RELAY INCLUDING AN ACTUATINGCOIL CONNECTED WITH SAID RESET SWITCH FOR ENERGIZATION, AND AN ARMATUREHAVING FIRST AND SECOND POSITIONS; SAID RESET RELAY BEING ENERGIZED WHENSAID RESET SWITCH IS PLACED IN ITS CLOSED POSITION; THE ARMATURE OF SAIDRESET RELAY ASSUMING ITS FIRST POSITION UPON ENERGIZATION OF SAID RESETRELAY; THE ARMATURE OF SAID RESET RELAY BEING COUPLED WITH THE ARMATUREOF SAID SHUT OFF RELAY SO THAT THE ARMATURE OF SAID SHUT OFF RELAYASSUMES ITS FIRST POSITION WHEN SAID RESET RELAY IS ENERGIZED AND THEARMATURE OF SAID RESET RELAY ASSUMES ITS SECOND POSITION WHEN SAID SHUTOFF RELAY IS ENERGIZED.